Custom control property, Datacolumn problem

[drey8]

I am having a hard time finding how to add a collection to a custom property. I am extending the treeview to be bound to a datasouce.
i have a datasouce property ( datatable ) and i would like another property that allow me to choose the datacolumns i would like to use(from the datasouce above).
i have no problem with the datasource property but the datacolumns i do not know how to add. Can any one help?

thank you
drey